First Reply Time - Average

We've got a question about the reports we are using within Insights. We want to show the Average First Reply time. This is not a problem, because we've created a metric for this (with the help of the Zendesk support documents).

But we would like to show the average First Reply time where we don't want to count 10% of the tickets which are having the largest first Reply time. As an example:

In this case we want to see the average First Reply time where we don't want to count number 01 (10 hours). This value affects the average and we would like to give them a realistic view, compared with the total average.

Do you have any idea in which way we could accomplish this report within GoodData?